495 results about "Neutral point voltage" patented technology

The invention provides a low current grounding single phase earth fault diagnosis method, comprising: capturing A voltage to ground, B voltage to ground, C voltage to ground, neutral point current and entire waveform information of each zero sequence current from a steady state to a transient state then to steady state when neutral point voltage exceeds presupposed threshold; first diagnosing whether being single phase earth fault, PT fusing, ferro resonance, arc suppressing coil resonance overvoltage, or neutral point overvoltage disturbance caused by experiment; selecting lines for the earth fault. The inventive method makes full use of steady state information and transient information of electric network before and after fault, and judges the fault and selects lines according to the long term changing rule of the neutral point voltage, which is different from the traditional stable state line selecting method and the transient line selecting method, thereby being suitable for the neutral point unearth electric network and the neutral point arc suppressing coil earth electric network at the same time, and well adapts the condition of complex site, thereby ensuring fault diagnosis and correct line selection.

Power from a high voltage battery (10) (for example 36V) is supplied through an inverter (12) to a motor generator (14). A low voltage battery (20) (for example 12V) is connected through a reactor (18) to the neutral point of the motor generator (14). A voltage ratio of the low voltage battery (20) to the high voltage battery (10) is preferably from 1:2 to 1:4. In order to set the neutral point voltage to a desired charging voltage into the low voltage battery (20), the inverter (12) is controlled so as to follow a current distortion phenomenon. In this way, in a dual-power source system with a voltage ratio of a low voltage battery (20) to a high voltage battery (10) between 1:2 and 1:4, voltage switching means for use in charging a charge voltage of a high voltage side into a low voltage source can be implemented at low cost.

The invention discloses a brushless direct-current motor stator flux linkage identification method. The method comprises the following steps: the neutral point of a brushless direct-current motor is grounded to make the voltage of the neutral point clamped to zero; the brushless direct-current motor end voltage is determined through the on-off state of a power tube and a fly-wheel diode during the normal conduction process and the commutation process of a three-phase full-bridge inverter, wherein a three-phase phase voltage is obtained by performing subtraction between the three-phase end voltage and the neutral point voltage; detection is performed by adopting a current sensor to obtain a three-phase phase current, and calculation is performed according to the voltage model of the stator flux linkage to obtain a three-phase stator flux linkage; the three-phase stator flux linkage is filtered by a high-pass filter through CLARK transformation; and vector synthesis is performed on the three-phase stator flux linkage filtered by the high-pass filter to obtain a brushless direct-current motor stator flux linkage. According to the invention, advantages of less required motor parameters, simple structure, less calculation amount and low hardware cost can be realized.

A power conversion method comprising detecting a three-phase source voltage of the three-phase AC power supply every control sampling cycle. The three-phase source voltage is allocated to a maximum voltage, an intermediate voltage and a minimum voltage as seen from a virtual neutral point voltage. A one-phase fixing switching mode is detected for fixing one of output phases into a predetermined state without switching and switching the other phases during a PWM cycle or a full phase switching mode for switching all of the phases during the PWM cycle based on an output voltage command and the three-phase source voltage. ON / OFF pattern of a bidirectional switch is determined from the switching mode thus selected, the output voltage command and the three-phase source voltage. The bidirectional switch is turned ON / OFF based on the ON / OFF pattern.

Problems with accuracy reading position detection signal peaks and minute phase differences in the detection current make motor drive control easily susceptible to differences in motor characteristics. The rotor position is determined based on whether or not a neutral point difference voltage, which is the difference voltage between the neutral point voltage and the pseudo-neutral-point voltage when the motor phases are selectively energized, exceeds a specific threshold value. The phase energized to start the motor is determined based on this determination and the motor is energized accordingly to start. Instead of switching directly from the search step at the initial rotor position to the back-EMF voltage mode, a search and start mode that creates initial rotor speed sufficient to start the motor is executed before entering the back-EMF voltage mode.

The invention provides a method for controlling a brushless direct current motor. The method comprises the following steps that S1, the open loop of the brushless direct current motor is controlled to be started; S2, after the brushless direct current motor is started, the comparison signal of the three-phase end voltage and the neutral point voltage of the brushless direct current motor is detected; S3, the zero crossing point signal of the brushless direct current motor is judged according to the comparison signal of the three-phase end voltage and the neutral point voltage; S4, the position and the rotating speed of the rotor of the brushless direct current motor are obtained according to the zero crossing point signal of the brushless direct current motor; S5, the brushless direct current motor is controlled according to the position and the rotating speed of the rotor of the brushless direct current motor. According to the method for controlling the brushless direct current motor, position detection does not need to be carried out through a position sensor, the size and weight of the brushless direct current motor can be reduced, the development cost of the motor can be lowered, the motor can be controlled to be operated at high speed, and the reliability of motor operation can be improved.

Problems with accuracy reading position detection signal peaks and minute phase differences in the detection current make motor drive control easily susceptible to differences in motor characteristics. The rotor position is determined based on whether or not a neutral point difference voltage, which is the difference voltage between the neutral point voltage and the pseudo-neutral-point voltage when the motor phases are selectively energized, exceeds a specific threshold value. The phase energized to start the motor is determined based on this determination and the motor is energized accordingly to start. Instead of switching directly from the search step at the initial rotor position to the back-EMF voltage mode, a search and start mode that creates initial rotor speed sufficient to start the motor is executed before entering the back-EMF voltage mode.

To a neutral point of a motor is connected a positive electrode of an auxiliary battery and an auxiliary load. Voltage on a power supply line to the auxiliary load, a neutral point voltage, is detected, and disconnection of the auxiliary battery is determined when an increase of ripples in the neutral point voltage is detected. When a voltmeter cannot be used, control of the neutral point voltage is continued by measuring current of the auxiliary battery and performing control such that the current value becomes 0. A resolver is further provided on the motor for detecting the rotor angle with high accuracy. A control circuit generates, in accordance with an output of the resolver, a voltage control signal for each phase current having the same amplitude as the carrier amplitude during startup, and compares the voltage control signal to carrier to obtain a gate signal having the same frequency as the carrier frequency. In switching of the inverter, due to this gate signal, periods in which all phases are on or off are reduced, thereby preventing a large neutral point current.

Problems with accuracy reading position detection signal peaks and minute phase differences in the detection current make motor drive control easily susceptible to differences in motor characteristics. The rotor position is determined based on whether or not a terminal difference voltage, which is the difference voltage between the motor terminal voltage and the pseudo-neutral-point voltage when the motor phases are selectively energized, exceeds a specific threshold value. The phase energized to start the motor is determined based on this determination and the motor is energized accordingly to start. Instead of switching directly from the search step at the initial rotor position to the back-EMF voltage mode, a search and start mode that creates initial rotor speed sufficient to start the motor is executed before entering the back-EMF voltage mode.